The traditional Hall-Heroult method has still been employed in aluminum electrolysis industry so far and cryolite-aluminum oxide has served as the basic system for electrolyte all the time, and in this system, sodium hexafluoroaluminate is usually used as cryolite. The temperature of electrolysis in aluminum electrolysis industry is about 960° C., which leads to high consumption of power, this is mainly because of high primary crystal temperature of electrolyte, besides, in order to keep good solubility of aluminum oxide, the degree of superheat at a particular temperature needs to be kept.
The method for industrially preparing potassium fluoroaluminate (potassium cryolite) mainly is chemical synthesis method: fluoroaluminate is generated by the reaction between anhydrous hydrofluoric acid and aluminum hydroxide, then reacted with potassium hydroxide at high temperature, and finally filtered, dried, molten and crushed to obtain potassium fluoroaluminate product; the potassium fluoroaluminate, which is synthesized using such a method, has a relative molecular weight of 258.28, a molecular formula of mKF.AlF3 (m=3.0) and a melting point of 560-580° C. The potassium cryolite prepared using the current industrial synthesis methods generally has a molecular ratio m between 2.0 and 3.0, so it is difficult to prepare low-molecular-ratio potassium cryolite, which is pure and extremely low in water content and has a molecular ratio m between 1.0 and 1.5.
Therefore, the shortcomings like high power consumption in electrolysis and unsatisfactory electrolyte exist in the prior art.